Marcus Terentius Varro (116-27 BC) in his (lost) Antiquitates rerum humanarum et divinarum established a distinction of three kinds of theology: civil (political) (theologia civilis), natural (physical) (theologia naturalis) and mythical (theologia mythica). The theologians of civil theology are "the people", asking how the gods relate to daily life and the state (imperial cult). The theologians of natural theology are the philosophers, asking for the nature of the gods, and the theologians of mythical theology are the poets, crafting mythology. The terminology entered Stoic tradition and is used by Augustine of Hippo.
Natural theology, thus, is that part of the philosophy of religion dealing with describing the nature of the gods, or, in monotheism, arguing for or against attributes or non-attributes of God, and especially the existence of God, purely philosophically, that is, without recourse to any special or supposedly supernatural revelation.
"Then was not non-existence nor existence: there was no realm of air, no sky beyond it. What covered in, and where? and what gave shelter? Was water there, unfathomed depth of water? Death was not then, nor was there aught immortal: no sign was there, the day's and night's divider. "
Marcus Terentius Varro (116–27 BC) in his Antiquitates rerum humanarum et divinarum established a distinction of three kinds of theology: mythical, civil (political) and natural (physical), of which the latter is concerned with the question "what are the gods". Varro's solution is a materialist (Epicurean) reduction of the gods to effects in the physical world (physikos). St. Augustine of Hippo quotes Varro frequently in his De civitate Dei, translating Varro's physikos with Latin naturalis.
Plato gives the earliest surviving account of a "natural theology", in his Laws establishing the existence of the gods by rational argument. Aristotle in his Metaphysics argues for the existence of an "unmoved mover", an argument taken up in medieval scholastics.
From the 8th century, the Mutazilite school of Islam, compelled to defend their principles against the orthodox Islam of their day, looked for support in philosophy, and are among the first to pursue a rational Islamic theology, called Ilm-al-Kalam (scholastic theology). The teleological argument was presented by the early Islamic philosophers, Alkindus and Averroes (founder of Averroism), while Avicenna (founder of the Avicennism school of Islamic philosophy) presented both the cosmological argument and ontological argument in The Book of Healing (1027).
Thomas Aquinas (c.1225–1274), wrote Summa Theologica and Summa Contra Gentiles which both present various versions of the Cosmological argument and Teleological argument, respectively. The Ontological argument is also presented, but rejected in favor of proofs dealing with cause and effect alone.
John Ray (1627–1705) also known as John Wray, was an English naturalist, sometimes referred to as the father of English natural history. He published important works on plants, animals, and natural theology.
William Derham (1657–1735), was a friend and disciple of John Ray. He continued Ray's tradition of natural theology in two of his own works, The Physico-Theology, published in 1713, and the Astro-Theology, 1714. These would later help influence the work of William Paley (see below).
In An Essay on the Principle of Population, the first edition published in 1798, Thomas Malthus ended with two chapters on natural theology and population. Malthus—a devout Christian—argued that revelation would "damp the soaring wings of intellect", and thus never let "the difficulties and doubts of parts of the scripture" interfere with his work. (Interestingly, Malthus' work would later be cited as inspiration by both Charles Darwin and Alfred Russel Wallace.)
William Paley gave a well-known rendition of the teleological argument for God. In 1802 he published Natural Theology, or Evidences of the Existence and Attributes of the Deity collected from the Appearances of Nature. In this he described the Watchmaker analogy, for which he is probably best known. Searing criticisms of arguments like Paley's are found in David Hume's posthumous Dialogues Concerning Natural Religion.
Thomas Paine wrote the definitive book on the natural religion of Deism, The Age of Reason (1794–1807). In it he uses reason to establish a belief in Nature's Designer who man calls God. He also establishes the many instances that Christianity and Judaism require us to give up our God-given reason in order to accept their claims to revelation.
Professor of chemistry and natural history, Edward Hitchcock also studied and wrote on natural theology. He attempted to unify and reconcile science and religion, focusing on geology. His major work in this area was The Religion of Geology and its Connected Sciences (Boston, 1851).
The Gifford Lectures are lectures established by the will of Adam Lord Gifford. They were established to "promote and diffuse the study of Natural Theology in the widest sense of the term—in other words, the knowledge of God." The term natural theology as used by Gifford means theology supported by science and not dependent on the miraculous.
Debates over the applicability of teleology to scientific questions came to a head in the nineteenth century, as Paley's argument about design came into conflict with radical new theories on the transmutation of species. In order to support the canonical scientific views at the time, which explored the natural world within Paley's framework of a divine designer, The Earl of Bridgewater, a gentleman naturalist, commissioned eight Bridgewater Treatises upon his deathbed to explore 'the Power, Wisdom, and Goodness of God, as manifested in the Creation.' They first appeared during the years 1833 to 1840, and afterwards in Bohn's Scientific Library. The treatises are:
In response to the claim in Whewell's treatise that "We may thus, with the greatest propriety, deny to the mechanical philosophers and mathematicians of recent times any authority with regard to their views of the administration of the universe", Charles Babbage published what he called The Ninth Bridgewater Treatise, A Fragment. As his preface states, this volume was not part of that series, but rather his own reflections on the subject. He draws on his own work on calculating engines to consider God as a divine programmer setting complex laws underlying what we think of as miracles, rather than miraculously producing new species on a Creative whim. There was also a fragmentary supplement to this, posthumously published by Thomas Hill.
The works are of unequal merit; several of them took a high rank in apologetic literature, but they attracted considerable criticism. One notable critic of the Bridgewater Treatises was Edgar Allan Poe, who wrote Criticism. Robert Knox, the anatomist, referred to them as the "Bilgewater Treatises"; he was an idealist, and disliked the detailed and utilitarian explanations of the Treatises. The joke became commonplace, and can be found in Charles Darwin's correspondence.
The Bridgewater Treatises